By development of the WWW (World Wide Web), a system of WWW is widely used in LANs ("Local Area Networks") is called an of a company. A user can access information stored in a WWW server by giving a specified URL (Uniform Resource Locator) through a WWW the browser. The information displayed by browser includes link data to resource and screen layout data and it is described by HTML (Hyper Text Makeup Language). An HTML document must be described by a special grammar and the user cannot create the document easily. However, recently, the HTML document is created by converting a document file through a format conversion means.
Data transmission between WWW server and WWW browser as a client is controlled by HTTP (Hyper Text Transfer Protocol). When the browser requests the server to transmit the HTML document, the browser sets a communication session to the server. Then, the browser sends an identifier (data discrimination information) and data transmission request to the server. After the browser receives the data from the server, the communication session is completed. The browser stores the data in memory section (Hard Disk). Hereafter, when the data is requested by the user, the browser directly accesses the data from the memory section. In short, the browser includes a cache memory function to raise the data presentation speed. Furthermore, even if the communication session is not linked to the browser, the server can repeatedly access the data from the memory section.
In case a plurality of users commonly work through each terminal while the document is displayed on each terminal, a technique for each terminal to efficiently support the work of the users is explained. In the support system to share the document among the plurality of users, the document indicated by one user (one terminal) is sent to other users (other terminals) by a communication control section. In the other terminals, received data is displayed to inform to the user. Furthermore, if the data shared in the plurality of terminals is changed, the change data is transmitted among the plurality of terminals. In each terminal, the sharing data is updated at realtime.
Each terminal includes a group-communication control section. The group-communication control section of one terminal sets communication session (link) to at least two terminals. By broadcasting function, the data is sent to the linked other terminals in one time. If all terminals are connected to same communication system (coaxial cable, wireless of same frequency), the data (packet) is sent to all terminals as destination. In each terminal, a received packet is analyzed. If a group-identifier of the packet coincides with a group-identifier to which the terminal belongs, the received packet is processed. In this method, the data is transmitted to the specified plurality of terminals at the same time. In comparison with a method to respectively send the data to each terminal, processing time is greatly reduced.
As mentioned above, in proportion to development of the system such as WWW in company, sharing of HTML documents in realtime is desired. One prior method of sharing of HTML documents in a plurality of terminals is explained in detail. As shown in FIG. 1, assume that three users X, Y, Z respectively have a terminal (communication control apparatus). These three terminals are linked to each other. Therefore, the three users X, Y, Z can communicate through each terminal. As shown in FIG. 2, three terminals X, Y, Z and WWW server W are connected to a network L. In a program of each terminal, a browser process and a data sharing process are included. Assume that the user X requests new hyper text to the browser W by indicating URL of the hypertext. In this case, a communication session is set between the terminal X and the server W. The server W retrieves the hypertext from its memory (not shown in FIG. 2) by using URL and transmits the hypertext to the browser of terminal X. When the browser of terminal X receives the hypertext, the communication session to the server W is completed. At the same time, in the terminal X, the obtaining of the message of the hypertext of the URL is informed to the data sharing process through DDE (Dynamic Data Exchange) as a communication means between processes. The hypertext data is stored in the memory section of the terminal X and analyzed. Then, screen data is created from the hypertext data and displayed in the terminal X. The data sharing process in the terminal X obtains URL as hypertext discrimination information from information of process communication, creates a packet consisting of the hypertext sharing order and the hypertext discrimination information, and broadcasts the packet to the terminals Y, Z. On the other hand, the data sharing process in the terminals Y, Z analyzes the received packet, obtains the hypertext sharing order and URL, and supplies the hypertext obtaining indication to the browser process. The browser requests the server W to obtain the hypertext according to the URL. After obtaining the hypertext, the hypertext is displayed. If an arbitrary terminal of the terminals X, Y, Z has the hypertext in its memory section, the arbitrary terminal processes the hypertext without request for the server W. If the server W does not exist not inside a company as INTERNET but outside as INTERNET, as an INTRANET, but outside as an INTERNET server, a groupware Proxy server is used in the INTRANET. After receiving the hypertext sharing order, the browser in the terminal connects to the groupware Proxy server. The. Proxy server obtains the indicated data from the server W and supplies the obtained data to the terminal. Therefore, in each terminal, the time from request for data to display the data is reduced. However, in the prior art, the following three problems occur.
(1) All browsers in all terminals are not always connected to the WWW server or the groupware Proxy server. A situation that a terminal can not access the data occurs. The reason for this is that the number of terminals to simultaneously connect is limited or a connection request from the terminal is rejected according to the situation.
(2) Performance of the WWW server and the groupware Proxy server falls. The reason for this is that each terminal simultaneously requests the data to the WWW server or the groupware Proxy server.
(3) The time from request for data to display the data increases in proportion to number of terminals. The reason for this is that the browser of each terminal respectively obtains the data from the WWW server. For example, in the case of N existing terminals, data is transmitted at N-times. A response time falls in proportion to the number of terminals sharing the data.